1.6
1 A module location field ( 2 characters ).
2 A measurement value field ( 6 characters ).
3 An engineering units field ( 3 characters ).
4. A user defined message ( UDM ) field ( 6 characters ).
The module location field defines whether the process variable represents an internal
transducer or an external analogue input. The letter ’I’ indicates an internal gas sensor
module. The letter ’E’ indicates an external analogue input. The letter is followed by
a number defining the gas sensor module site number.
The measurement field is a 6 character number representing the concentration
measured by an internal transducer or the scaled analogue input value. Should the
measured value for a transducer exceed 120% of the specified full scale deflection for
that transducer then the measurement field is replaced by the word ‘OVER’ to indicate
that the transducer is in over range condition.
The engineering units field is a user defined 3 character message identifying the units
of measurement. For Gfx transducers the user is offered a choice of the units to be
displayed. The options available are volume parts per million ( vpm ) or mg per normal
cubic meter. For paramagnetic oxygen transducers the displayed unit is fixed as
volume percent.
The user defined message ( UDM ) field represents the component name of the
process variable.
The xentra display may be returned to measurement display at any time by pressing the
'MEASURE' key ( see figure 1.4 ). If no user key presses are input then the Xentra
returns to the measurement display after a one minute time out. This time-out is
extended to 20 minutes during the calibration options.
When first powered up, the display will show a sequence of power up messages before
returning to the measurement display ( see section 2.12 ). If the user does not wish to
see the power up messages then these can be disabled by pressing the measure key
during the 'SYSTEM OK' message. The warming-up icon ( see figure 1.5 ) will also be
displayed until all gas sensor modules are at their respective operating temperature,
This may take up to 1 hour.
Icons located at the bottom centre of the measurement display indicate the status of the
instrument ( see figure 1.5 ). These icons show that the instrument is warming up or
being calibrated using the autocalibrate facility. Icons at the bottom of the display also
indicate the presence of alarms or faults. If the fault or alarm icons appear on the
measurement display the exact nature of the fault or alarm may be determined via the
user interface, (see 6.2 'Displaying alarms present' and 6.3 'Displaying faults present').
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